Seasonal variation of the cadmium content of Murex trunculus in a non-cadmium polluted environment

Previous studies had indicated that Calvi bay, Corsica, was unpolluted by cadmium but was subject to seasonal organic pollution from the tourist trade. However, high concentrations of cadmium had been reported in the mollusc Murex trunculus, collected from the bay, and a 2-year study has now been carried out on this phenomenon. Seasonal variations in the cadmium content of the soft tissues of Murex are discussed; the concentration increased from February to July, and then decreased again. The results suggested that cadmium could be an essential element for Murex and be implicated in the process of shell formation; its accumulation in the visceral mass preceded the formation of the shell and was facilitated by the presence of metallothioneins. The implications of these findings for the interpretation of the results of studies in pollution are indicated.